阅读下列短文，从每题所给的四个选项(A、B、C、D)中，选出最佳选项。

　　Why don't birds get lost on their long flights from one place to another? Scientists have puzzled over this question for many years．Now they're beginning to fill in the blanks．

　　Not long ago, experiments proved that birds depend on the sun to show them the way during daylight hours．But what about birds that mainly fly at night? Tests with man-made stars have shown that certain night-flying birds are able to follow the stars on their long-distance flights．

　　Once such bird-a warbler-had spent its lifetime in a cage and had never flown under a natural sky at night．Yet it showed an inborn ability to use the stars．The bird's cage was put under a man-made star-filled sky．The bird tried to fly in the same direction as its outdoor cousins．Any change in the position of the man-made stars caused a change in the direction of its flight．

　　Scientists think that warblers, when flying in daylight, use the sun for guidance．But stars are their main dependence of flying at night．What do they do when stars are hidden by clouds? They find their way by such landmarks as mountains, beaches and rivers．But when it's too dark to see these, the warblers circle helplessly, unable to get their directions．

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阅读理解。

　　When you are on your computer at home or at school, there are some very important things to keep in mind(脑子)．

　　◇Use the Internet when your parents tell you it's OK or you have to．

　　◇First, remember that never give out your information such as your name, home address, school name, or telephone number in a chat room．Also, never send your pictures to someone you chat with on the Internet．

　　◇Never write to someone who you feel is not good．

　　◇Do not meet anybody or invite them to visit you．

　　◇Tell your parents if you read anything bad on the Internet．

　　◇Remember that people online(网上的)may not tell you the truth．A“12-year-old girl” may be an old man!

　　◇Be polite when you use the Internet to send an e－mail or chat with somebody．

　　◇Tell your parents about the people you meet or talk to on the Internet．

　　◇Ask your parents to spend time with you, so you can show them the sites you like to visit．

　　The following form(表格)is some personal information of a middle schoo1 student, Li Ming．

　　He is online in his home．Tell him what he should do when he has the problems listed below according to the passage above．

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